Industry Voices—Heynen: What’s next for cable broadband networks?

The COVID-19 pandemic has certainly turned our world upside-down, as it represents a human tragedy affecting millions around the world. There have been countless acts of selflessness on a global scale as we all work to end the threat as quickly as possible.

From a data communications perspective, the pandemic has shown that networks are extremely resilient, particularly residential fixed broadband networks as well as the upstream aggregation of those networks. Though the early weeks of the pandemic in the U.S., downstream traffic during the day increases anywhere from 30% to 150% and upstream traffic at the same time increased nearly equally. Broadband networks handled these increases reliably.

Across all physical broadband media—PON, cable, and DSL—much of the stability can be attributed to the design of TCP algorithms, which allow for a fair distribution of access to bandwidth across all subscribers. Additionally, broadband networks have always been oversubscribed with additional headroom designed to support peak bursts well above the sustained bandwidth rates typically required by users.

Cable operators, who provide the vast majority of fixed broadband connections in the U.S., have employed a number of different strategies for handling both the initial burst of residential traffic, as well as the sustained usage levels they have experienced since the early stay-at-home mandates. Beyond taking advantage of existing TCP algorithms and using mechanisms like TCP ACK suppression to limit the total number of individual session requests, cable operators have been using additional DOCSIS tools to ensure the reliability and performance of their networks.

For example, operators that have deployed DOCSIS 3.1 modems in their networks have been turning on OFDM and OFDM-A carriers to increase throughput in both the downstream and upstream directions. Ensuring upstream bandwidth has become critical, given the rapid growth of videoconferencing, remote learning and online gaming.

In other cases, operators that had deployed switched digital video years ago are able to move more of their broadcast TV channels to their switched tiers and then re-allocating that spectrum to their DOCSIS services.

Other operators have been complementing these efforts with node splits in serving areas that have seen the biggest traffic spikes or where service group sizes were still at the high end of comfortable ranges for operators. But node splits have been more challenging to complete for some operators for a number of reasons ranging from labor shortages to difficulty securing site access.

When the smoke clears…

The actions taken by broadband providers to ensure the performance and reliability of their networks over the last two months have largely succeeded. However, nothing changes the simple fact that the amount of data traffic these networks have delivered has far exceeded in two months what most operators expect to deliver in a calendar year. That type of consumption is changing how operators think about architecting their networks, the peak and sustained usage models, over provisioning, and the upgrade cycles they can expect when equipment runs hotter and more consistently than it ever has before.

For cable operators, these new parameters have already resulted, or will result, in an accelerated investment cycle initially in order to accomplish two bandwidth-increasing goals:

• Splitting existing optical nodes to reduce service group size and increase downstream capacity for all users;

• Moving to mid-split or high-split architectures in order to increase upstream capacity.

In many cases, existing optical nodes were split once in conjunction with the rollout of DOCSIS 3.1 capacity in headends and hub sites. Now, because of the new capacity requirements as a result of the pandemic, operators are looking to segment a larger percentage of their node base, as well as further segmenting already-split nodes. We have already heard stories of operators accelerating their node split programs by anywhere from 6 to 12 months. Each node split typically results in a doubling of the DOCSIS channel licenses on existing CCAP platforms.

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Because there is an immediate need to bolster their broadband networks using the equipment they have in place today, the net result is that spending on cable access infrastructure in 2020 will be heavily-weighted towards traditional, centralized CCAP platforms. Thus, long-term strategic initiatives, such as a shift towards distributed access architectures (DAA) will take a back seat to the need to inject new capacity into the networks now.

Separate from traditional node splits is the initiative being undertaken at a growing number of operators to push fiber deeper into their networks to support an expansion of upstream capacity. Although a number of major initiatives were already planned or underway prior to the pandemic, the rapid increase in upstream utilization rates due to stay-at-home orders has only accelerated operators’ timelines.

Most operators are still providing return band of 5 MHz to 42 MHz. Using a mid-split design can push the upper limits of that band to 85 MHz, with a high split design giving operators up to 204 MHz to work with in the return path. Some large operators have already started or completed their transition to mid-split, while others are jumping directly to a high-split architecture. At 204 MHz, cable operators can offer 1Gbps of upstream bandwidth, which matches what many telcos are offering through their FTTH networks.

But these upstream upgrades also require significant changes to the outside plant, including amplifiers and taps. For many cable operators, this isn’t necessarily a bad thing, as these critical outside plant components are nearing the end of their lifespan over the next five years, after having served in broadband networks for the last 10-20 years. Additionally, the replacement of these devices as part of mid-split architectures also help lay the groundwork for the eventual deployment of DOCSIS 4.0 and Extended Spectrum DOCSIS (ESD).

Though these upgrades put a lot on the plates of cable operators worldwide, the combination of all these transitions will ultimately lead to the complete overhaul and modernization of their broadband access networks, as they continue to migrate down the path towards 1.8 GHz spectrum, Extended Spectrum or Full Duplex DOCSIS modulation, DAA, and virtualization. Again, all these changes will definitely occur in phases, as each operator weighs the vision of their future networks and services against the short- and long-term costs to get there.

Jeff Heynen is senior research director for broadband access and home networking at Dell'Oro Group. He joined Dell’Oro Group in 2018, and is responsible for the broadband access and home networking market research program. While at the firm, Heynen has expanded the broadband access and home networking coverage areas. Heynen’s research and analysis has been widely cited in leading trade and business publications. Heynen is a frequent speaker at industry conferences and events, including Broadband World Forum, CES, FoE Japan, FTTH Conference, and the SCTE Cable-Tec Expo. He can be reached at; follow him @JeffHeynen.

Industry Voices are opinion columns written by outside contributors—often industry experts or analysts—who are invited to the conversation by FierceTelecom staff. They do not represent the opinions of FierceTelecom.